The present invention relates to a packing material for chromatographic separations and to a method of manufacturing the same. More particularly, the present invention relates to a packing material for liquid chromatography produced by mixing a carbon product, such as carbon black with a synthetic resin and/or a pitch component, granulating the mixture, and heat treating the resultant granules. The present invention also relates to methods of chromatographic separation that employ the granules.
Conventionally, packing materials for liquid chromatography have included silica gel materials and synthetic resin-based materials. However, problems such as chemical stability, including solubility, have resulted in silica gel-based materials exhibiting poor durability as a packing material.
In chromatography and other separation methods, there is a certain amount of selectivity that is necessary in order for the stationary phase to separate the various components in a mixture. For this reason, carbon products, such as carbon black, have not been used as a standard stationary phase in separation systems because carbon is a strong non-specific adsorbent. This has been disappointing in the past, because carbon products, otherwise, would have many advantages over commercially available adsorbents. For instance, there are no corrosion problems with carbon products nor are there any swelling problems with carbon products. In addition, carbon products can be subjected to large temperature ranges and/or extreme pressures which would be beneficial for certain types of adsorptions, such as temperature swings used in some types of chromatography. In addition, with certain separation processes used in the production of biopharmaceuticals for clinical applications, the sterilization requirements or recommendations provide for the use of hot sodium hydroxide. With such sterilization procedures, the current separation devices such as silica columns, cannot be used. Further, the polymeric columns such as cellulose polymers, are chemically but not physically stable to such sterilization treatments.
U.S. Pat. No. 5,270,280 relates to the use of carbon black packing materials for liquid chromatography, wherein the carbon blacks have specific dimensional ratios, specific particle diameters and surface areas, and specific micropore volumes. The patent is incorporated herein in its entirety by reference. The methods of making the packing material according to U.S. Pat. No. 5,270,280 include granulating a carbon black-containing mixture and heat-treating the granules at a high temperature in the range of from 800° C. to about 3000° C., in an inert atmosphere. The high temperature heat-treatment is most likely necessary to carbonize and graphitize the binder material in order to form a graphitic layer. According to the patent, if the temperature is below 800° C., the graphitization of the binder is not sufficient, resulting in the packing material having insufficient strength. While the patent describes the packing material as providing improved mechanical durability and separating characteristics, a need still exists for an improved liquid chromatography packing material that has improved mechanical durability and improved separating properties.
It is desired to provide an improved liquid chromatographic packing material and a method of producing such a material which does not require a high temperature heat-treatment or graphitization step.
In addition, it is desired to provide a method of chromatographic separation that provides improved separation of sample components.